Roof structures of reinforced temperature-hardenable plastic and process for making same

ABSTRACT

A SELF-STANDING ROOF STRUCTURE IS ERECTED OVER A BUILDING BY INITIALLY FORMING THE ROOF STRUCTURE OF FLEXIBLE, HEATHARDENABLE PLASTIC MATERIAL. AFTER ANCHORING ITS PERIMETER TO FORM A SUBSTANTIALLY AIR-TIGHT SPACE BENEATH IT, THE FLEXIBLE ROOF STRUCTURE IS INFLATED AND SUPPORTED BY AIR PRESSURE, AND WHILE SO SUPPORTED THE PLASTIC MATERIAL IS HARDENED BY APPLYING HEAT. THIS HARDENING IS ACCOMPLISHED BY PROVIDING HOT GASES BENEATH THE INFLATED ROOF OR ALTERNATIVELY BY FEEDING HOT FLUID THROUGH DUCTS IN HEAT EXCHANGE RELATIONSHIP WITH THE ROOF OR BY A COMBINATION OF THESE HEATING ACTIONS. THE DUCTS THEMSELVES MAY DESIRABLY BE FORMED OF HEAT-HARDENABLE PLASTIC MATERIAL SO THAT THEY BECOME ARCH-SHAPED ROOF BEAMS INCLUDED IN THE SELF-STANDING ROOF FOR STRENGTHENING IT. HEATABLE CONDUCTING ELEMENTS MAY BE IMBEDDED IN OR AFFIXED TO THE ROOF PANELS TO SUPPLY HEAT FOR CURING THE PLASTIC AND LATER ON TO BE USED FOR MELTING SNOW TO PREVENT UNDUE SNOW LOADS. THESE MAY BE ELECTRICALLY HEATED OR PLASTIC TUBE CONDUCTING ELEMENTS OF EACH DIAMETER FOR CARRYING HEATED FLUID SUCH AS HOT WATER. WHILE AIR SUPPORTED STRUCTURES HAVE BECOME WELL KNOWN FOR VARIOUS USES, PRIMARILY TEMPORARY IN NATURE, THIS INVENTION CAN BE CLASSED AS AN &#34;AIR-ERECTED&#34; STRUCTURE OR AN &#34;AIR-ERECTED&#34; ROOF STRUCTURE INTENDED FOR PERMANENT USES.

"D. M CRACKEN C: 3,557,515 ROOF STRUCTURES OF REINFORCED TEMPERATURE-HARDENABLE I Jan, 26,1971

PLASTI CAND PROCESS FOR MAKING SAME Filed April 20, 1967 .01..)111-1 NVENTOR. Calm/n A Mac CraMe/z United States Patent U.S. Cl. 52--741 7 Claims ABSTRACT OF THE DISCLOSURE -A self-standing roof structure is erected over a building by initially forming the roof structure of flexible, heatharden-able plastic material. After anchoring its perimeter to form a substantially'air-tight space beneath it, the flexible roof structure is inflated and supported by air pressure, and while so supported the plastic material is hardened by applying heat. This hardening is accomplished by providing hot gases beneath the inflated roof or alternatively by feeding hot fluid through ducts in heat exchange relationship with the roof or by a combination of these heating actions. The ducts themselves may desirably be formed of heat-hardenable plastic material so that they become arch-shaped roof beams included in the self-standing roof for strengthening it. Heatable conduct ing elements may be imb'edd'ed in or aflixed to the roof panels to supply heat for curing the plastic and later on to be used for melting snow to prevent undue snow loads. These may be electrically heated or plastic tube conducting elements of small diameter for carrying heated fluid such as hot water. While air supported structures have become well known for various uses, primarily temporary in nature, this invention can be classed as an air-erected structure or an air-erected roof structure intended for permanent uses.

'The present invention relates to roof structures of reinforcedtemperature-hardenable plastic and the process for making such roof structures. The concept of this invention also extends to the building apparatus employing this invention.

Among the many advantages provided by the present invention are those resulting from the fact that it enables a large area of floor space, a sports arena, an ice skating rink, and the like to be covered with a permanent roof structure in a brief period of time with a minimum of labor. Moreover, the completed roof structure is self standing so that the enclosed area may be free of internal columns.

In accordance with the invention, a fabric web is assembled in an arch shape corresponding with the desired configuration of the completed roof structure. This fabric web is covered or impregnated with a temperature hardenable plastic material and the periphery of the reinforced plastic is anchored in place on a foundation at the desired location of the building. Before the reinforced plastic is hardened, the region beneath it is filled with air under slight pressure so as to support the reinforced plastic roof temporarily. After the roof is thus fully inflated and supported, the plastic material is hardened by heating for completing the self-standing roof structure.

The various features, aspects and advantages of the roof structures and process of the present invention will become more fully understood from a consideration of the following specification in conjunction with the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a building embodying the present invention, and illustrating the process for making same;

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FIG. 2 is a cross-section taken along the line 22 through the roof of FIG. 1 and shown on enlarged scale;

FIG. 3 is a sectional elevational view of a building structure in which the roof is supported at its perimeter by wall means and also illustrates a modified process for making the roof structure;

FIG. 4 is a cross-section taken along the line 44 through the roof structure of FIG. 3 and shown on enlarged scale; and

FIG. 5 is a cross-section of a roof similar to that shown in FIG. 2 and wherein the roof panels include heatable conducting elements.

As shown in FIGS. 1 and 2 the roof 10 includes an initially flexible fabric web 12 coated and impregnated with a plastic material 14 which is capable of being permanently hardened by the action of heat. Thus, the fabric serves as a reinforcing web within the plastic. For example, the polyester resin-coated fabric web which is available from American Cyanamid Co. of Wallingford, Conn, under the trade designation called Instant Pipe may be used to advantage. This resin has a curing time of approximately fifteen minutes when heated to a temperature in the range of 250 to 260 F. The plastic-coated web 12 is secured together as by heavy sewing to form a large panel which is corrugated, as shown in FIG. 2.

The fabric web 12 is constructed of inert material having a suitably high tensile strength, for example such as glass fibers, glass fiber cloth, nylon fibers, a fine stainless steel wire mesh, or similar high strength fibers, mesh, or the like.

In making the roof 10 as shown in FIG. 1 the perimeter of the roof is anchored at the desired location, for example in making a roof having an arch shape, the two edges of a corrugated roof panel are secured to a pair of spaced, parallel footings 16 and 18 so that the corrugations extend in the plane of the arch to provide a rigid structure. The two edges of the roof structure are secured to the footings 16 and 18 in substantially air-tight relationship to form a substantially air-tight interior space.

In this embodiment an anchoring wire material 20 is imbedded in the footings when they are poured so that an upstanding anchor is available to be secured to the edge of the roof panel. For providing a substantially air-tight seal a large flap 22 extends down and inwardly along the floor of the building 24. The roof structure includes a pair of arch-shaped end panels 26 which are secured to the main panel. These end panels 26 may also be corrugated to provide added stiffness against wind loads, and they are anchored to the foundation in air-tight relationship.

At this time the, plastic material is flexible, and in order to support the roof in the desired shape, the airtight interior 27 is inflated with a pressurized gas flow '29, for example by operating a large blower 28 having its discharge nozzle 30 directed into the structure. The excess of the interior air pressure over the ambient pressure existing outside of the building raises the roof to the position shown in FIG. 1, and while it is thus inflated and supported, the resin is cured by heating.

In this illustrative embodiment the curing is accomplished by heating the interior air up to a temperature which exceeds the hardening temperature of the plastic, thus heating the plastic from the interior air. As shown, a combustion heating device 32, for example, an aircraft type of jet engine is employed as a powerful heater recirculator 32 and it is mounted upon a wheeled chassis 34. The air within the inflated roof is heated rapidly and recirculated violently by operating this stationary jet engine at high input. The tail pipe '36 is curved and directed vertically to increase the tendency of the hot gases 37 to rise up within the air-tight roof structure so that the hot gases flow up directly and immediately into contact with the interior of the roof to maximize the heat exchange action for heating the roof." The tail pipe 36 is of suflicient diameter so that the velocity of the gas discharge 37 is not unduly high.

In this process the hot gases are replenished and maintained at a temperature above the hardening temperature of the plastic until the desired hardening or curing of the plastic material has been carried out by this heating process. Then the inflation blower 28 may be shut off and'it may be removed along with the heater recirculator 32. The blower and heater may be used at other building'sites for repeating the process.

The building 24 structure is now completed and is read to be used as a sports arena, ice skating rink, fair ground, protected storage area, or the like. It will be understood that the ground may be covered by a suitable floor, such as a concrete slab, and then the building may be furnished on the interior with partitions for use as oflice space, apartment units, and so forth. The corrugations in the roof structure strengthen and stiffen it as will be understood.

The modified embodiment of the invention as shown in FIGS. 3 and 4 includes a roof structure A in which a plurality of strips of plastic-coated web material 40 are secured to the main roof panel, for example as by sewing to form a plurality of ducts 42. The roof edges are secured to and supported by a pair of sill beams 43 extending along and secured to the tops of a pair of parallel walls 44 and 46, which are shown as constructed of cinder blocks, resting upon concrete footings 16 and 18.

The roof structure is flexible initially and is inflated by a large blower 28 having its discharge nozzle 30 directed through the wall 44 for supplying a pressurized air flow 29 into the interior 27A of the building 24A. After the roof is inflated it is hardened by heating by means of hot gases.

In order to apply the heat at a point high up near the roof by providing a stratified region S of very hot gas directly beneath the roof, a modified jet engine heater 32 has a tail pipe 36A which is curved and extends up into the vicinity of the roof for supplying the hot gases 37. Also, there is an intake duct 48 which extends and opens up into the region of the stratified hot gases S for recirculating and reheating this stratified mas of gases S while minimizing the over-all heating of the air within the building near ground level.

For augmenting the heating action being applied to the roof each of the individual ducts 42 and the adjacent region of the main roof panel is hardened by flowing a hot fluid through the duct itself. In this example, the hot fluid which is sent through the ducts 42 is superheated dry steam provided by a portable steam generator 50 having a steam hose line 52 adapted to be connected to the ends of the ducts 42. The opposite end of the duct is left open so that the hot steam can flow therethrough from end to end and issue herefrom as indicated at 54. The residual heat in the discharged steam 54 serves to increase the temperature of the stratified layer S. After the ducts 42 have become hardened they form a multitude of roof beams each having an arch shape conforming to the roof 10A and greatly increasing its strength and rigidity.

As soon as the plastic 14 in the roof 10A is fully cured by heating, then the pieces of construction equipment 28, 32 and 50 are turned off and removed for use elsewhere. The building 24A may be finished off on the interior in any suitable manner, as described above in connection with FIGS. 1 and 2, depending upon the desired use.

It is to be understood that the combustion heating device 32 as shown in FIG. 1 or FIG. 3, being a jet engine, is turbine driven, and that in various construction projects it may be advantageous to use combustion heating devices 32 having different structures and configurations. For example, the combustion heating device 32 may include a blower and a burner powered by a suitable prime mover such as a gasoline engine, diesel engine, or electric motor, and in certain installations the heating device 32 may comprise a burner employing natural draft combustion. The fuel may be any convenient inexpensive combustible material such as oil, kerosene, gasoline or gas.

4 Inor der to provide additional protection in case of heavy snow storms or strong wind storms, the blower 28 which was used to inflate the roof structure may be left in place as a permanent installation to be turned on if ever such extreme weather conditions should occur. Turning on this blower raises the-internal air pressure, thus'helping to support the snow load until it is dissipated and helping to resist deflection of the roof structure when subjected to the forces of a powerful wind. I

Inviting attention again to FIG. 4 it is to be noted that the. ducts 42may have any desired configuration including oval and circular. The resin material 14 of these ducts may be a different material from the resin 14 in the roof panels 10A. For example, the resin 14 in the ducts may be a stronger material curing'at a higher temperature such as supplied by steam curing or the like. On the other hand the resin 14 in the roof panels 10A would. not have to have the same degree of strength and therefore can be a lower temperature curing resin. In some cases the curing temperature of the resin 14 in the panels of the roof 10A might even be so low as to be cured by the heat of the sun over a relatively longer period of time, while the ducts 42 are cured by the high temperature fluid circulated therethrough.

In those cases where the roof panels themselves require a higher degree of heating than from the sun alone the entire ducted roof structure 10A can be hardened by using hot fluid from the supply device 50, relying upon heat supplied from the ducts 42, without using the recirculating heater 32. However, the fastest curing is obtained by using both of the devices 32 and 50 when constructing roof structures having hardenable duct beams incorporated therein. 1

In another form of the invention I have included heatable conducting elements 58 (FIGS. 4 and 5) as a part of the roof structure. These heatable conducting elements 58 are shown as being imbedded in the plastic resin matrix 14 near to the web 12, but it is to be understood that they may be affixed to the underside of the fabric web 12. The elements 58 are used in hardening and curing the roof structure initially and thereafter they are used in melting and dissipating snow to prevent undue snow loads during the lifetime of the building 24 or 24A.

These heatable conducting elements 58 may be heating wires for conducting electricity in the form of a suitable grid extending throughout the area of the roof. A source of the energy medium to be conducted through these elements 58 is shown at 60 connected through supply lines 62 to the grid of elements 58.

In a further embodiment of the invention, these conducting elements 58 are flexible plastic-tubing of small internal diameter, for example in the range from of an inch to of an inch which are afiixed to the underside of the fabric web 12. A hot fluid such as hot water is pumped from the source 60 through the lines 62 and is circulated through a grid of the conducting tubing 58 for curing and hardening the roof structure and at a later time for melting snow.

The arch-shaped roof structures, it will be appreciated, may be of any suitable arch shape such as hemispherical, arch shaped, vaulted, and the like. v

The terms and expressions which I have employed'are used in a descriptive and not a limiting sense, and I have no intention of excluding equivalents of the invention described and claimed. v V I A What is claimed is: v

1. The process of making a self-standing roof structure over a protected space cornprising the steps of building a wall along the boundary of the vdesired protected space, forming .a roof structure of flexible, heat-hardenable plastic material, anchoring the perimeter of said roof structure to the top of said wall to forrna substantially air-tight interior space beneath said flexible roof structure, supplying air to said interior space at a pressure exceeding the ambient air pressure existing outside thereof for 'inflating and supporting said flexible roof structure in the desired shape above the level of the top of said wall, heating said roof structure by creating a mass of stratified hot gases immediately beneath the inflated roof structure and replenishing and maintaining said stratified mass by continuously withdrawing hot gases from said stratified mass, reheating the withdrawn gases and returning them to the mass, and thereby heating and curing the hardenable plastic material in said roof structure while minimizing the heating of the air near the floor level within said wall.

2. The process of making a self-standing roof structure over a protected space comprising the steps of formingv an air-supportable flexible roof structure of flexible fabric web coated with heat-hardenable plastic material; providing a plurality of heatable fluid medium conducting ducts of flexible heat-hardenable plastic material secured to said roof structure and extending across said roof structure and being in heat exchange relationship with said hardenable plastic material; anchoring the perimeter of said roof structure at the desired location to form a substantially air-tight interior space beneath said flexible roof structure while maintaining the ends of said ducts open; supplying air to said interior space at a pressure exceeding the ambient air pressure existing outside of said space for inflating and supporting said flexible roof structure; while maintaining the roof thus supported, feeding a heating fluid medium through each of the conducting ducts from end to end for heating the roof structure to a temperature above the hardening temperature of said plastic material; continuing to feed the heating fluid medium through each conducting duct until the desired hardening of the plastic material in heat exchange relationship therewith has occurred; and thereby hardening said ducts into rigid selfstanding beams secured to said hardened roof structure.

3. The process of making a self-standing roof structure as claimed in claim 2 in which said conducting elements are ducts of relatively large diameter and said heating medium is superheated dry steam which is fed through said ducts.

4. The process of making a self-standing roof structure as claimed in claim 2 including the steps of Supplying hot gasses to the interior space beneath the inflated roof structure creating a mass of stratified hot gases immediately beneath the inflated roof structure in heat exchange relationship with the hardenable plastic material thereof, said hot gases being at a temperature above the hardening temperature of said plastic material for aiding in hardening said plastic material, and replenishing and maintaining said stratified mass during the hardening thereof by continuously withdrawing hot gases from said stratified mass, reheating the withdrawn gases and returning them to said mass.

5. The process of making a self-standing roof structure over a protected space comprising the steps of forming an air supportable roof structure of flexible, heat-hardenable plastic material, providing said flexible roof structure with a plurality of ducts including heat hardenable plastic material in the structure of said ducts, anchoring the perimeter of said air supportable roof structure at the desired location to form a substantially air-tight interior space beneath said roof structure, supplying air to said interior space at a pressure exceeding the ambient air pressure existing outside thereof for inflating and supporting said flexible roof structure in the desired shape, heating said flexible roof structure, feeding hot fluid through said ducts, and supporting said roof structure by maintaining the pressure in said interior space exceeding ambient pressure thereby hardening the plastic material of said roof structure and in the duct structure by said hot fluid to form a rigid self-standing roof and to form said ducts into selfstanding beams of the roof structure.

6. The process of making a self-standing roof structure as claimed in claim 5 wherein said ducts are supported in an arch shape by maintaining the pressure in said interior space exceeding ambient pressure, and hardening the plastic material in said duct structure to form arch-shaped self-standing beams of the roof structure.

7. The process of making a self-standing roof structure as claimed in claim 5 wherein' the hot fluid which is fed through said ducts is superheated dry steam.

References Cited UNITED STATES PATENTS 2,649,101 8/1953 Suits 52-2 2,812,769 1'1/1957 Schaefer et al 52----2 3,111,569 11/ 1963 Rubenstein 522X 3,139,464 6/1964 Bird et al. 26432 3,170,828 2/ 1965 Irvine 522X 3,235,712 2/1966 Watson 219-213X 3,277,219 10/ 1966 Turner 52-2 3,282,533 11/1966 Spain 522X 3,292,338 12/1966 MacClarence et a1. 522X ALFRED C. PERHAM, Primary Examiner US. Cl. X.R. 

